Hydrogen peroxide oxidation degradation of a low-rank Naomaohu coal

A mild controllable oxidation method was developed to depolymerize the macromolecular aromatic clusters of NMH coal into water-soluble products (WSPs) without ring-open reaction. Hydrogen peroxide (H 2 O 2 ) was employed to oxidize coal sample at 60 °C, and the effect of reaction time on coal conversion and oxidation products was studied. The results showed that H 2 O 2 is able to break bridge bonds and side chains connected to aromatic clusters, while C ar -C ar bonds of arene keep unchanged at same conditions. After 10 h oxidation, the coal conversion is 83.4 wt% and the aromaticity of oxidation residue is 7.43%, indicating most of aromatics have transferred to WSPs. The aromatic ring distribution in WSP can reflect that of NMH coal to some extent, where 1-ring, 2-ring and 3-ring compounds account for 58.4 mol%, 19.9 mol% and 21.7 mol%, respectively. Moreover, the pyrolysis of NMH coal and oxidation residue was conducted on an online pyrolysis-vacuum ultraviolet photoionization mass spectrometry , and the oxidation of several typical model compounds was also carried out to understand the oxidation mechanism. The results showed that the PhO-RPh bonds between aromatic clusters are most easily destroyed by H 2 O 2 . H 2 O 2 oxidation degradation of coal are accompanied by generation of alkenes and decarboxylic reaction.